Solar device for autonomous refrigeration by solid-gas sorption

ABSTRACT

A device is provided for the autonomous production of refrigeration approximately 40° C. lower than ambient temperature from a low-temperature solar thermal source, the device including: (i) a reactor arranged to cool and/or heat the solid reagent; (ii) a condenser; (iii) a first tank for storing the liquid refrigerant at ambient temperature; (iv) an enclosure arranged to store a phase-change material and also including an evaporator; (v) a second tank for storing the liquid refrigerant at a low temperature; (vi) apparatus for conveying the refrigerant and (vii) apparatus for controlling the flow of the refrigerant.

TECHNICAL FIELD

The present invention relates to a solar device for autonomousrefrigeration.

The present invention lies in the fields of self-contained solar airconditioning and self-contained solar cooling.

STATE OF THE PRIOR ART

The use of solar energy for refrigeration is particularly suitable forrefrigeration on isolated sites in regions with hot climates and/or thatdo not have access to the power grid and/or where energy supply iscostly.

A number of techniques are known that enable the production ofrefrigeration either concomitant with the availability of day-time solarenergy, or out of phase, during the night.

The current solutions are mainly based on compressor technologies, whichconsume large amounts of electricity and use refrigerants with highgreenhouse warming potential. For isolated sites, these solutionsresult, for example, in electricity being produced by generators thatuse a fuel stored in tanks, or in electricity produced during the day byphotovoltaic panels being stored in a fleet of batteries. Thesesolutions require, as appropriate, large amounts of maintenance,frequent replenishment of fuel (weekly to monthly), periodic replacementof the battery fleet (every two to five years), and sophisticatedelectronic control and command devices (controllers, inverters, etc.).

More particularly, a first technique for producing refrigeration duringthe day consists of converting solar radiation either into electricityvia photovoltaic collectors or into work via a thermodynamic enginecycle such as for example an organic Rankine engine cycle, in order thento supply a reverse thermodynamic cycle for refrigeration by expansion(Stirling cycle) or vaporization of a refrigerant (reverse Rankinecycle).

A second method consists of directly using solar radiation in thermalform to supply a gas sorption method of the liquid/gas absorption type,which requires the circulation of a binary or saline solution, such asthe ammonia/water or water/lithium bromide solutions conventionallyused. Such devices are for example described in U.S. Pat. No. 4,207,744and U.S. Pat. No. 4,184,338.

These techniques are however relatively complex and costly to implementand require in particular sophisticated control and command proceduresfor said refrigeration method, particularly circulation pumps andcompressors to circulate the working fluids, and/or require low ambienttemperatures (below 35° C.) to refrigerate efficiently. Theseconstraints affect the reliability and robustness of these methods.

Another technique is based on methods for the sorption of a gaseousrefrigerant by an active solid. These are for example thermochemicalmethods or adsorption methods. The drawback of such methods lies in thesolid nature of the sorbent materials used; they operate discontinuouslyand lead to intermittent refrigeration, as described for example in U.S.Pat. No. 4,586,345, U.S. Pat. No. 4,993,234 and WO 86/00691.

The object of the present invention is to at least overcome a largenumber of the problems set out above and also to result in otheradvantages.

Another purpose of the invention is to solve at least one of theseproblems by means of a new refrigeration device.

Another purpose of the present invention is autonomous production ofrefrigeration.

Another purpose of the present invention is to reduce the costs ofrefrigeration.

Another purpose of the present invention is to reduce the pollutionassociated with refrigeration.

Another purpose of the present invention is to produce refrigerationmore reliably and robustly.

Another purpose of the present invention is to reduce the maintenancedemands associated with refrigeration.

DISCLOSURE OF THE INVENTION

At least one of the aforementioned aims is achieved with a device forautonomous refrigeration from a low-temperature solar thermal sourcebetween 50° C. and 130° C., said refrigeration being produced with atemperature difference 5° C. to 40° C. lower than the ambienttemperature of the outdoor environment and said device implementing amethod for the thermochemical sorption of a refrigerant by a solidreagent, said device comprising:

-   -   a reactor arranged to contain the solid reagent and comprising        at least one heat exchanger to cool and/or heat the reactor,    -   a condenser capable of liquefying the gaseous refrigerant coming        from the reactor,    -   a first tank for storing the liquid refrigerant produced by the        condenser at ambient temperature,    -   an enclosure arranged to store a phase-change material and also        comprising an evaporator in direct contact with said        phase-change material and capable of evaporating the liquid        refrigerant,    -   a second tank for storing the liquid refrigerant at a        temperature lower than ambient temperature, and working in        conjunction with the first tank on the one hand and the        evaporator and the reactor on the other hand,    -   at least one means of conveying the refrigerant arranged to        circulate said refrigerant in liquid or gaseous form between the        reactor, the first tank, the second tank and the evaporator,    -   at least one means of controlling the flow of the refrigerant        acting on the means of conveying the refrigerant, said at least        one control means being arranged to regulate the flow of the        refrigerant independently as a function of the pressures        prevailing in the reactor, the first and second tanks, the        condenser and the evaporator.

Preferably, the refrigeration produced by the device according to theinvention is at a temperature of between −10° C. and 20° C.

The device according to the invention and the variants thereof describedbelow make it possible to efficiently achieve both the solar heating ofthe reactor and the cooling of the condenser during the course of theday, and the cooling of the reactor during the course of the night.

The completely autonomous management of the day-time and night-timephases without active control is a promising solution for meetingrefrigeration requirements on isolated sites in regions with hotclimates that do not have access to the power grid. The device accordingto the invention also makes it possible to reduce production costs asthere is no costly external energy supply. Furthermore, as it does notuse any consumables, the maintenance of the device—which is limited tooccasional cleaning of the collectors—is greatly reduced andinexpensive.

The device according to the invention also makes it possible to reducethe pollution associated with refrigeration as it can use a refrigerantthat has no impact on the ozone layer or global warming. Furthermore,the device does not generate greenhouse gases or deplete fossil energyresources as it only uses thermal solar energy, which is a widelyavailable renewable energy. Furthermore, the device according to theinvention is completely silent, which is a significant advantage inurban environments or in exceptional and/or protected areas.

Finally, the device according to the invention does not have any movingmechanical parts, which thus makes it possible to reduce both theoperating sound level and the wear on the components and risk of fluidleaking from dynamic sealing gaskets; the device according to theinvention is more reliable.

It is also more robust due to its entirely autonomous operation thatautomatically adjusts to the external insolation and temperatureconditions. As it does not have any control/command and/or electroniccontrol components, it has a very long service life; the reactivecomposites used in the reactors of the device according to the inventionhave been tested over more than 30,000 cycles (corresponding toapproximately 80 years of daily operation) without any loss ofperformance being observed.

By way of non-limitative examples, the refrigerant can be selected fromwater, ammonia, ethylamine, methylamine or methanol, and the solidreagent can be selected for example from calcium chloride (CaCl₂),barium chloride (BaCl₂) or strontium chloride (SrCl₂). More generally,the device according to the invention preferably uses a refrigerantother than hydrochlorofluorocarbons and chlorofluorocarbons, whichdeplete the ozone layer and contribute to global warming.

The phase-change materials used in the present invention to efficientlystore the refrigeration produced by solidifying are preferably organicor inorganic compounds. By way of non-limitative examples, they can forexample be water, an aqueous solution or a paraffin.

The means for controlling the flow of the refrigerant advantageouslymake it possible to regulate said flow passively, solely as a functionof the pressure differences prevailing between the reactor, thecondenser, the evaporator and the first and second tanks during theday-time regeneration and night-time refrigeration phases.

Advantageously, the enclosure and/or the second tank can be thermallyinsulated in order to reduce the energy requirements necessary tomaintain the temperature inside and maintain a liquid refrigeranttemperature lower than the ambient temperature during the day, thuspreventing the temperature of the refrigerant contained in theevaporator from increasing over the course of the day.

Preferably, the evaporator can be supplied with liquid refrigerant fromthe second tank by the difference in density of said refrigerant betweenthe inlet and outlet of said evaporator. This thermosyphon operationmakes it possible generate a flow of refrigerant between the second tankand the evaporator without a pump and without an external energy supply,thus enhancing the autonomy of the device according to the invention.

Preferably, the reactor can also comprise an isothermal housing arrangedto contain the heat exchanger and/or the reactor and capable of reducingthe heat losses of said reactor, particularly by conduction. Theinsulation may be obtained by any known insulating means that withstandsthe temperature variations to which the reactor is subjected during thecourse of the night and the day, such as for example glass wool or rockwool.

Advantageously, the reactor can be made up of a plurality of tubularelements comprising the solid reagent and connected to each other bysaid means of conveying the refrigerant in order to make maximum use ofthe solar radiation and optimise the heating of the reactor. It isadvantageous to maximise both the solar absorption area and theorientation of said reactor in relation to the sun. The tubular elementconfiguration thus makes it possible to maximise both the active area ofthe reactor and the direct incidence of the sun on said reactor.

Preferably, the plurality of tubular elements can be coated with asolar-absorbing coating to improve the thermal efficiency of theplurality of tubular elements, said coating being in close contact withthe wall of the plurality of tubular elements.

By way of non-limitative examples, the coating can be a simple solarpaint or a metal film (copper, aluminium, etc.) with good thermalconductivity, placed in thermal contact with the wall of the tubularelements and on which a selective thin layer can be deposited.

Advantageously, the solar-absorbing coating can have low infraredemissivity.

According to a particular embodiment, the reactor can also comprise atleast one covering element transparent to solar radiation, arranged toreduce heat losses and maximise solar collection efficiency, said atleast one covering element extending beyond the surface of the reactorexposed to the sun.

Optionally, the at least one covering element can also be opaque toinfrared radiation in order to enhance the greenhouse effect.

Preferably, at least one of the surfaces of the reactor not exposed tothe sun can be thermally insulated to reduce heat losses. The insulationmay be obtained by any known insulating means, such as for example glasswool or rock wool.

According to a particular embodiment, the reactor can also compriseactuation means in order to orient the plurality of tubular elements ofthe reactor in a plane substantially perpendicular to the direction ofthe sun and thus present the maximum possible solar-absorbing area, inorder to optimise the orientation of the reactor and maximise the solarcollection efficiency and the associated heat exchanges.

According to a first version of the device according to the invention,the night-time cooling of the reactor is provided by natural circulationof the air in the reactor, thus making it possible to achieve cooling ina totally passive manner.

Advantageously for this first version, the reactor can also comprise atleast one flap for the ventilation of the plurality of tubular elements,said at least one flap being located at the top and/or bottom of saidreactor.

Preferably, the at least one ventilation flap can be arranged to sealthe reactor when it is in the closed position in order to enhance theheat exchanges inside said reactor.

Advantageously, the at least one ventilation flap can also comprisedrive means to open/close it.

According to a first variant, the drive means can consist of a low-powerelectric motor.

Advantageously, the electric motor can be powered by an electricityproduction and/or storage device, optionally powered by photovoltaicpanels.

According to a second variant, the drive means can consist of a rack andpinion device actuated by a compressed air rotary jack connected to acompressed air reserve.

Preferably, the compressed air reserve can be refilled by an aircompressor powered by photovoltaic panels.

According to a third variant, the drive means can consist of a rack andpinion device actuated by a single-acting hydraulic linear jackcontrolled by a thermostat bulb in thermal contact with an absorbingplate exposed to the sun. This last variant is entirely passive,autonomous in terms of energy and automatically controlled.

Preferably, the plurality of tubular elements can also comprise aplurality of circular fins, the base of which is in close thermalcontact with the wall of the tubular elements in order to enhance theheat exchanges.

Advantageously, the plurality of fins can be covered with asolar-absorbing coating to enhance the heat exchanges.

Advantageously, the plurality of tubular elements can be arrangedhorizontally in order to improve the flow of air around said tubularelements.

Preferably, the condenser can be of the finned tube type and cooled, inthe day, by natural convection of the air around said finned tubes.

According to a second version of the device according to the invention,the night-time cooling of the reactor can be provided by a heat pipeloop operating as a thermosyphon and comprising:

-   -   a working fluid capable of performing thermodynamic work,    -   a so-called heat pipe evaporator, working in conjunction with        the plurality of tubular elements of the reactor and arranged to        evaporate the working fluid and absorb the heat released by the        reactor,    -   a so-called heat pipe condenser, working in conjunction with the        evaporator and the reactor, said condenser being arranged to        liquefy the working fluid and perform a heat transfer with the        outside air,    -   a working fluid tank arranged to store said liquid working fluid        and enable the optimum filling of the at least one tubular        element of the reactor with working fluid,    -   a passive autonomous device for controlling the flow of the        working fluid in the heat pipe loop comprising:        -   a first working fluid flow control means, located between            the working fluid tank and the bottom of the at least one            means of conveying the working fluid, said first control            means being arranged to control the supply of liquid working            fluid to the at least one means of conveying the working            fluid,        -   a second working fluid flow control means, located between            the outlet of the heat pipe evaporator and the heat pipe            condenser, arranged to control the movement of the gaseous            working fluid in the at least one means of conveying the            working fluid.

This second version of the cooling of the device according to theinvention thus makes it possible to efficiently achieve both the heatingof the reactor during the day and the cooling of firstly the reactorduring the night and secondly the gaseous refrigerant flooded condenserin the working fluid tank of the heat pipe loop.

Preferably, the working fluid is selected from those fluids that have aboiling temperature at atmospheric pressure of between 0 and 40° C. andthat have a pressure of between 1 and 10 bar in the temperature rangefrom 20 to 100° C. By way of non-limitative example, it can be a typeC4, C5 or C6 paraffinic hydrocarbon (such as butane, methylpropane,pentane, methylbutane, dimethylpropane, hexane, methylpentane,dimethylbutane, etc.), an HFC type working fluid conventionally used inorganic Rankine cycles (R236fa, R236ea, R245fa, R245ca, FC3110, RC318,etc.), an inorganic fluid (ammonia, water), or an alcohol (methanol,ethanol, etc.).

Advantageously, the device according to this second embodiment can alsocomprise a valve for starting the heat pipe loop, arranged to fill saidheat pipe loop with working fluid and/or drain it.

Preferably, the heat pipe evaporator can comprise at least one means ofconveying the working fluid arranged inside the plurality of tubularelements of the reactor and in close thermal contact with the solidreagent, said at least one means of conveying the working fluidassociated with each tubular element being connected to each other bymanifolds at the top and bottom.

Advantageously, the plurality of tubular elements of the reactor can beinclined vertically in order to facilitate the movement of the workingfluid by simple gravity.

Advantageously, the heat pipe condenser can be made up of at least onefinned tube connected to each other by means of conveying the workingfluid.

Preferably, the at least one finned tube of the condenser can bearranged substantially horizontally at the rear of the reactor, with aslight tilt to enable the gravity flow of the liquefied working fluid tothe working fluid tank.

Preferably, the working fluid tank can be arranged to maintain a minimumworking fluid level in the means of conveying said working fluid ofbetween one third and three quarters of the height of a tubular elementof the reactor.

The working fluid tank can also be arranged to evaporate the refrigerantand also comprises the refrigerant condenser arranged to liquefy saidrefrigerant.

Advantageously, the device for controlling the working fluid flow in theheat pipe loop can also comprise at least one autonomous control means,arranged to respectively open and close the first and second workingfluid flow control means, for example at the start of the night and thestart of the day.

Preferably, the at least one autonomous control means of the first andsecond working fluid flow control means can comprise:

-   -   an absorbing plate capable of absorbing solar radiation and        emitting in the infrared, said absorbing plate being arranged to        heat by means of day-time solar radiation and cool during the        night,    -   a thermostat bulb in thermal contact with the absorbing plate,        comprising a fluid capable of expanding under the effect of a        temperature variation,    -   a connecting element working in conjunction firstly with the        thermostat bulb and secondly with the first and/or second        working fluid flow control means, said connecting element being        arranged to open or close said working fluid flow control means.

According to another embodiment of the invention compatible with each ofthe previous variants, the device according to the invention can consistof a modular architecture comprising:

-   -   a plurality of first assemblies each comprising:        -   the reactor made up of a plurality of tubular elements and            comprising the heat exchanger,        -   the condenser capable of liquefying the refrigerant,        -   the tank for storing the refrigerant at ambient temperature,            the volume of which corresponds to the volume of the            plurality of tubular elements of said first assembly,        -   refrigerant flow control means,    -   a second assembly comprising:        -   the enclosure arranged to store a phase-change material and            comprising thermal insulation,        -   the second tank for storing the liquid refrigerant at a            temperature lower than ambient temperature and comprising            thermal insulation,        -   the evaporator for evaporating the refrigerant, located in            the enclosure and working in conjunction with the second            tank,        -   first means of controlling the flow of refrigerant between            the evaporator and the second tank,        -   second means of controlling the flow of refrigerant to            ensure the connection between the second assembly and the            plurality of first assemblies.

This modular arrangement makes it possible to facilitate theimplementation and installation of the device.

Advantageously, the evaporator can be of the flooded type and compriseat least one tubular element arranged to circulate the refrigerant bythermosyphon with the second tank.

Preferably, the second assembly can comprise a tight isolation valve,arranged to fill the device with refrigerant and/or drain it.

Preferably, the refrigerant can be ammonia.

According to another aspect of the invention, it is proposed that thedevice according to the invention be used to produce ice.

Alternatively, the device according to the invention can also be used toproduce water.

Advantageously, water can be produced by condensing the water vapourcontained in the air on a wall that is kept cold by the device.

DESCRIPTION OF THE FIGURES AND EMBODIMENTS

Other advantages and characteristics of the invention will becomeapparent from the following description and from several embodimentsgiven as non-limitative examples with reference to the attachedschematic drawings, in which:

FIG. 1 shows a Clausius-Clapeyron diagram of the thermodynamic states ofthe components of the device according to the invention over the courseof the two main phases,

FIG. 2 shows a schematic diagram of the thermochemical refrigerationdevice according to the invention,

FIG. 3 shows the day-time phase of the operation of the device accordingto the invention, consisting of a solar regeneration and energyproduction phase,

FIG. 4 shows the night-time phase of the operation of the deviceaccording to the invention, consisting of a refrigeration phase,

FIGS. 5a and 5b respectively show side and front diagrams of a reactorcomprising the heat exchanger of the device according to the inventionin a first embodiment wherein the night-time cooling is provided bynatural convection,

FIG. 6 shows a particular method of autonomous control of a ventilationflap for the day-time heating and night-time cooling of the reactoraccording to the invention,

FIG. 7 shows a diagram of a reactor comprising the heat exchanger of thedevice according to the invention in a second embodiment wherein thenight-time cooling is provided by a heat pipe loop,

FIGS. 8a and 8b respectively show the day-time state and the night-timestate of an autonomous control means of the first and second means forcontrolling the flow of the working fluid in the heat pipe loop,

FIGS. 9a, 9b and 9c respectively show front, side and detailed diagramsof a particular embodiment of a reactor comprising the heat exchangeraccording to the invention and cooled by a heat pipe loop,

FIG. 10 shows a particular embodiment of the invention wherein theautonomous refrigeration device has a modular design,

FIG. 11 shows a diagram of the refrigeration module of the deviceaccording to the invention,

FIGS. 12a, 12b and 12c respectively show front, longitudinalcross-sectional and transverse cross-sectional views of an evaporator ofthe modular device according to the invention.

The embodiments which will be described below are in no way limitative;it is possible in particular to imagine variants of the inventioncomprising only a selection of characteristics described below inisolation from the other characteristics described, if this selection ofcharacteristics is sufficient to confer a technical advantage or todifferentiate the invention with respect to the state of the prior art.This selection comprises at least one, preferably functional,characteristic without structural details, or with only a part of thestructural details if this part alone is sufficient to confer atechnical advantage or to differentiate the invention with respect tothe state of the prior art.

In particular, all the variants and all the embodiments described can becombined together if there is no objection to this combination from atechnical point of view.

In the figures, the elements common to several figures retain the samereference.

The Refrigeration Method

The method for intermittent solar refrigeration described below and theobject of the present invention is a thermochemical sorption thermalmethod the principle of which is based on the combination of aliquid/gas change of state of a refrigerant G and a reversible chemicalreaction between a solid reagent and this refrigerant:

S ₁ +G _((Gas)) ⇄S ₂ Q _(R) and G _((Liq)) +Q _(L) ⇄G _((Gas))

In the case of the synthesis reaction of the solid S₂ from left toright, the refrigerant gas G reacts with the refrigerant-lean saltreagent S₁ to form the refrigerant-rich salt S₂. This reaction isexothermic and releases heat of reaction Q_(R). Furthermore, the gas Gabsorbed by S₁ is produced by evaporation of the refrigerant liquid G byabsorbing the latent heat Q_(L).

In the reverse direction from right to left, the endothermicdecomposition reaction of the solid S₂ requires the thermal gain Q_(R)so that the reagent S₂ releases the refrigerant gas G again. It is thencondensed by releasing latent heat Q_(L).

These processes are implemented in two connected tanks that exchange therefrigerant gas G, thus forming a thermochemical dipole wherein thefirst tank, made up alternately of the evaporator or the condenser, isthe seat of the change of state of the refrigerant G. The second tank ismade up of the reactor and contains the solid reagent salt reactingreversibly with the refrigerant G.

The physico-chemical processes implemented in such a thermochemicalmethod are monovariant and, with reference to FIG. 1, the thermodynamicequilibria implemented over the course of the two main phases of themethod according to the invention can be represented by straight linesin a Clausius-Clapeyron diagram:

Ln(P)=f(−1/T)

Each of the straight lines shown in FIG. 1 describes the change intemperature T and pressure P at the thermodynamic equilibrium of eachelement forming the device according to the invention (reactor,condenser, tanks, evaporator) that will be described in the paragraphsbelow.

The step of regeneration of the thermochemical dipole takes place athigh pressure Ph imposed either by the reactor heating conditions duringdecomposition or by the refrigerant condensation conditions. Conversely,the refrigeration step takes place at low pressure Pb imposed by thereactor cooling conditions during synthesis and the refrigerationtemperature Tf produced at the evaporator.

Description of the Device According to the Invention

To implement this thermochemical method with a solar thermal source, thesimplest device according to the invention comprises the followingelements, listed with reference to FIG. 2:

-   -   a reactor 202 in which the solid reagent is confined, equipped        with at least one heat exchanger 201 for the heating and cooling        of the reactor 202 and comprising means 203 of conveying the        refrigerant to the condenser 207 or the evaporator 212;    -   a condenser 207 equipped with a first tank 208 storing the        condensed liquid refrigerant 217 at ambient temperature;    -   an evaporator 212 supplied for example by thermosyphon, i.e. by        the difference in density of the refrigerant between the liquid        inlet 218 and the two-phase outlet 219 of said evaporator 212,        by means of a second tank 209 that can be thermally insulated        from the external environment and contains the liquid        refrigerant at the temperature of the refrigeration produced.        The evaporator 212 is placed in an enclosure 215 that is also        thermally insulated;    -   refrigerant flow control means 204, 205 and 206, such as for        example check valves, enabling the autonomous management of the        refrigerant flows. The control means 204, 205 on the one hand        and 206 on the other hand respectively make it possible to        regulate the flow of the refrigerant in gaseous form on the one        hand and liquid form on the other hand. If there is a pressure        difference upstream and downstream of said control means 204 to        206, then the valves are open. By way of example, for the        so-called gaseous valves 204 and 205, a pressure difference of        less than 100 mbar can be preferable to ensure, in the day,        slightly higher pressure in the reactor 202 relative to the        condenser 207, and, at night, slightly lower pressure in the        reactor 202 relative to the evaporator 212. Conversely, for the        valve 206 installed on the liquid connection between the first        208 and second 209 tanks, a pressure difference corresponding to        the difference between the refrigerant condensation pressure and        evaporation pressure can preferably be chosen. By way of        example, this pressure difference can be in the region of 5 to        10 bar lower.

Operation of the Device

The solar refrigeration device 200 according to the invention thusinvolves the transformation of a consumable solid reagent arranged in areactor 202 and operates according to an intrinsically discontinuousmethod. It comprises two main phases that are described below withreference to FIGS. 3 and 4:

-   -   a day-time regeneration phase (FIG. 3) during which the reactor        202 is connected to the condenser 207. This phase consists of        heating the reactor 202 to a so-called high temperature Th, by        means of the incident solar thermal energy, thus making it        possible to decompose the charged salt S2 during the day. The        refrigerant gas G released by this reaction first condenses in        the condenser 207 at ambient temperature To and is then stored        in the first tank 208 in liquid, preferably condensed, form;    -   a night-time refrigeration phase (FIG. 4) during which the        reactor 202 is connected to the evaporator 212. This phase        consists of cooling the reactor 202 to ambient temperature To.        The evaporator 212 is the seat of the refrigerating chemical        reaction, pumping heat to the environment to be cooled on the        one hand and releasing the refrigerant gas G on the other hand.        The salt S1 contained in the reactor 202 then reabsorbs the gas        G coming from the evaporator 212 by releasing heat of reaction        to the environment at ambient temperature To. The refrigeration        produced then enables the solidification of a phase-change        material 213. By way of non-limitative examples, this can for        example be the production of ice or the solidification of a        paraffin. The phase-change material 213 thus makes it possible        to store the refrigeration produced at night in order to        redeliver it on demand throughout the day.

The operation of said autonomous solar refrigeration device 200 will nowbe described in detail over a daily cycle.

At the start of the day, the reactor 202 is at a temperature close tothe outside ambient temperature To and at a so-called low pressure Pb(point S in FIG. 1). It is then connected to the evaporator 212 (point Ein FIG. 1) producing refrigeration at a so-called cold temperature Tfand steam that is absorbed by the reactor 202. As the pressure in thereactor 202 is then slightly lower than the pressure in the tank 209 andthe evaporator 212, the pressure difference is slightly greater than thepressure of the valve 205. As day breaks, the reactor 202 is graduallyexposed to the sun and its temperature increases: it then starts todesorb the refrigerant gas G by decomposition of the reagent. Thepressure in the reactor 202 then increases and the pressure differencebetween the evaporator 212 and the reactor 202 decreases. When thepressure difference becomes lower than the opening pressure of the checkvalve 205, it closes and no longer allows this steam to transfer to thereactor 202. The closing of the check valve 205 makes it possible forthe pressure in the reactor 202 to increase more quickly (movement frompoint S to point D of the reactor along the straight line of equilibriumin FIG. 1). The benefit provided by the check valve 205 is that it makesit possible to maintain the cold temperature of the enclosure to berefrigerated by preventing the steam desorbed by the reactor 202 underthe action of the exposure of the reactor 202 to the sun from condensingin the evaporator 212 and increasing the temperature thereof again.

When the pressure in the reactor 202 becomes slightly higher than thepressure prevailing in the first tank 208 of condensed liquid at ambienttemperature To, the valve 204 opens in order to cool and condense thedesorbed gas leaving the reactor 202 to the temperature Th in thecondenser 207. The condensed gas is then stored throughout the day atthe day-time ambient temperature To in the first tank 208 (correspondingto point C in FIG. 1).

When, at dusk, the solar radiation is no longer sufficient, thetemperature prevailing inside the reactor 202 starts to decrease, thenleading to a reduction in the internal pressure of the reactor 202. Thepressure differential between the reactor 202 and the condenser 207decreases and, beyond a certain threshold, then becomes lower than theopening pressure of the valve 204. The valve then closes and isolatesthe reactor 202, thus preventing it from reabsorbing the steam containedin the first tank 208 at ambient temperature To. The reactor 202 iscooled to ambient temperature To, also leading to a reduction in theinternal pressure thereof in accordance with its thermodynamicequilibrium (corresponding to migration from point D to point S in FIG.1).

Depending on the equilibria and thresholds chosen, the refrigerationtemperatures Tf produced and the outside ambient temperature To, twodifferent embodiments for the cooling of the reactor 202 are proposedand described in the paragraphs below.

As the reactor 202 cools down, the pressure thereof then also becomeslower than the pressure prevailing in the second tank 209.Advantageously, this can be thermally insulated from the outside inorder to maintain the liquid refrigerant 218 contained in the tank 209at a temperature lower than ambient temperature during the day, thuspreventing the temperature of the refrigerant contained in theevaporator 212 from increasing over the course of the day. As a result,the pressure prevailing in the thermally insulated second tank 209 islower than the pressure prevailing in the uninsulated first tank 208.The pressure decrease then enables the valve 205, when a certainpressure difference corresponding to the valve opening threshold isreached, to open, thus permitting the reactor 202 to take in andchemically absorb the gas coming from the second tank 209.

The pressure then decreases in the second tank 209 and, when thepressure difference with the first tank 208 of condensed liquid issufficient, for example in the region of a few bar (typically 1 to 10bar), the valve 206 opens and supplies the second tank 209 with liquidat the night-time temperature To, until all of the condensed liquidrefrigerant contained in the first tank 208 has been decanted into thesecond tank 209 via the valve 206. As the reactor 202 continues toabsorb the steam produced by evaporation of the liquid contained in thesecond tank 209, the decanted liquid cools until the temperature thereofis lower than the temperature of the refrigerant contained in theevaporator 212 maintained at a higher temperature by the PCM 213.

Thereafter, circulation of the refrigerant is triggered naturally, bythermosyphon, using the difference in density of the liquid refrigerantbetween the evaporator 212 and the second tank 209. The evaporator 212is then supplied from the bottom 218 with liquid refrigerant that isdenser than at its diphasic outlet 219. The refrigerant leaving theevaporator 212 through the diphasic outlet 219 is made up of both aliquid phase and a gaseous phase, which makes it less dense than thesolely liquid refrigerant entering the evaporator 212. The steamproduced in the evaporator 212 is then sucked into the second tank 209and absorbed by the reactor 202 via the valve 205. The refrigeration isthus produced in the evaporator 212 throughout the night until sunrise,when the reactor starts to heat up; the refrigeration produced duringthe night is stored in the phase-change material 213 to be deliveredaccording to the refrigeration requirements during the day.

Solar Heating of the Reactor

To achieve efficient heating, the heat exchanger 201 of the reactor 202must have the largest possible solar absorption area. According to aparticular embodiment, the optimum orientation is obtained by aligningthe heat exchanger 201 with the direction normal to the sun, i.e. forexample tilted relative to the ground at an angle preferablycorresponding to a latitude close to the latitude of the site foroptimum refrigeration production throughout the year.

Such a heat exchanger 201, arranged to utilise solar radiation, will nowbe described with particular reference to FIGS. 5a and 5 b.

To utilise solar radiation to maximum effect, and according to aparticular embodiment, the heat exchanger 201 is coupled to the reactor202 and is made up of a set of tubular elements 501 comprising the solidreagent material 502. The tubular elements 501 aredistributed—preferably evenly—in an isothermal housing 503, and areconnected to each other by means of conveying 504—for examplemanifolds—and linked to the condenser 207 and/or the evaporator 212.

According to a particular embodiment, the tubular elements 501 arecovered with a solar-absorbing coating 505, if possible selective, inclose contact with the wall of the tubular elements 501. Thesolar-absorbing coating 505 has high solar absorptivity and,advantageously, low infrared emissivity.

A cover that is transparent to solar radiation 506 covering the frontsurface of the heat exchanger 201 exposed to the sun makes it possibleto reduce heat losses by convection. Preferably, it can also reduceradiation losses and enhance the greenhouse effect, by blocking theinfrared radiation emitted by reactors heated to a high temperature.Ultimately, the solar collection efficiency is maximized.

Advantageously, thermal insulation 507—for example using rock wool orglass wool—can be applied to the rear surface of the heat exchanger 201in order to reduce heat losses by conduction and/or convection to theexternal environment.

Night-Time Cooling of the Reactor

The night-time cooling of the reactor 202 can be achieved according totwo embodiments described below, the selection of which depends on thesolid reagent 502 used in the reactor 202, the temperature of therefrigeration Tf to be produced and the night-time ambient temperatureTo:

-   -   the first embodiment for cooling the reactor consists of natural        circulation of air in said reactor 202, by external cooling of        the tubular elements 501. This first embodiment can be        implemented when the solid reagent 502 makes it possible to        obtain a sufficiently large operating temperature difference        (typically greater than 20° C.) between the night-time outside        air temperature To and the stagnation temperature of the        reaction at the pressure imposed by the evaporation of the        refrigerant at Tf in the evaporator;    -   the second embodiment for cooling the reactor 202 consists of a        heat pipe loop operating as a thermosyphon; it is selected when        cooling by natural air circulation cannot be implemented.

Each of these two embodiments, together with all of the variants ofwhich they are comprised, are compatible with any one of the embodimentsof the invention set out above or below.

First Embodiment: Reactor Cooling by Natural Convection

FIGS. 5a and 5b respectively show side and front diagrams of a reactor202 comprising the heat exchanger 201 of the device 200 according to theinvention and according to this first embodiment of night-time coolingof said reactor 202 provided by natural air convection.

This cooling thus uses the air circulation caused by the stack effect inthe reactor 202 by means of opening the ventilation flaps located at thetop 509 and bottom 508 of the reactor 202.

Advantageously, to improve the heat exchanges and heat removal, thetubular elements 501 are equipped with fins 510, for example circular,the base of which is in close thermal contact with the wall of thetubular elements 501 of the reactor 202.

Advantageously, they can be arranged horizontally in order to improvethe heat convection coefficient by promoting an air flow substantiallyperpendicular to the direction of the tubular elements 501 in thereactor 202.

Finally, in order to absorb the solar radiation more efficiently, thefins 510 can be covered with a solar-absorbing coating in a similar wayto the coating that can cover the tubular elements 501.

In this first embodiment for cooling the reactor 202, the reactive gascondenser 207 can be of the finned tube type and placed at the rear orsaid reactor 202. It is then cooled during the day by natural convectionof the air on the finned tubular elements.

Each ventilation flap 508, 509 comprises a plate 511 arranged to beairtight on the frame of the reactor 202 during the day, and a rotatingrod actuated in particular at daybreak to close said flap 508, 509 andat nightfall to open said flap 508, 509.

According to an advantageous variant, the ventilation flap 508, 509 canalso comprise drive means 600 arranged to rotate it by means of variousdevices, controlled for example as a function of the detection ofdaybreak or nightfall, a temperature increase (thermostat device) or asolar irradiance threshold.

Different variants of these drive means 600 are proposed and describedin the paragraphs below. They are all compatible with any one of theembodiments of the invention set out above or below.

First Variant of the Ventilation Flap Drive

The ventilation flap 508, 509 can be driven using a low-power electricmotor that is, according to an advantageous variant, supplied by anelectric battery recharged by a photovoltaic collector. Typically, thepower requirements are sufficiently low and brief for the area of saidphotovoltaic collector to be less than one square metre.

Second Variant of the Ventilation Flap Drive

The ventilation flap 508, 509 can also be driven using a rack and piniondevice that can for example be actuated by a double-acting compressedair ¼-turn rotary jack. The rotary jack is then connected to acompressed air reserve (typically 6 bar) via a 5/3 or 4/3 monostablespool valve that is actuated over a short period (momentary controllasting approximately ten seconds) as a function of the solarirradiance. The closing of the ventilation flap is actuated when theirradiance is above a first threshold (obtained close to the moment whenthe sun rises) and the opening of the flap is actuated when theirradiance is below a second threshold (obtained close to the momentwhen the sun sets). Advantageously, the first closing threshold can begreater than the second opening threshold of said flaps.

The compressed air reserve can be refilled periodically by an aircompressor powered by photovoltaic panels.

Third Variant of the Ventilation Flap Drive

The ventilation flap 508, 509 can also be driven using the device 600described in FIG. 6. It is a rack and pinion device 601/602 actuated bya single-acting hydraulic linear jack 605 ultimately controlled by athermostat bulb 611 in thermal contact with an absorbing plate 612exposed to the sun.

The thermostat bulb 611 contains a fluid 613 that is sensitive totemperature variations. More particularly, the fluid 613 is capable ofvaporizing over a temperature range that is preferably between To and Thand corresponds to a pressure range compatible with the opening andclosing of the ventilation flap 508, 509 that it controls. Thevaporization of the fluid 613 makes it possible to pressurise thehydraulic liquid 606 contained in the hydraulic linear jack 605 by meansof an accumulator 608 containing a deformable bladder 609, working inconjunction with the thermostat bulb 611 and deformed by the fluid 613.

The hydraulic liquid 606 pressurized in this way makes it possible tomove both the piston 604 of the jack 605 and the rack 601, thus rotatingthe rod 620 of the ventilation flap 508, 509 by means of the drivepinion 602.

A return spring 603 makes it possible to push the hydraulic liquid 606back towards the accumulator 608 when the pressure in the thermostatbulb 611 decreases following reduced exposure of the solar-absorbingplate 612.

The quantity of fluid 613 contained in the thermostat bulb 611 isdefined as a function firstly of the volume of the bladder 609pressurizing the hydraulic liquid 606 of the jack 605, and secondly ofthe maximum pressure to be reached to actuate the ventilation flap 508,509, which must also correspond to an intermediate temperature Tibetween To and Th and at which there is no more fluid 613 to bevaporized.

The device according to this particular embodiment is entirely passive,autonomous and automatically controlled by the intensity of the solarradiation.

Second Embodiment: Reactor Cooling by Heat Pipe Loop

In this embodiment, the reactor 202 is cooled at night and/or therefrigerant condenser is cooled during the day by a heat pipe loop. Itis thus possible to transfer heat, firstly by evaporating a workingfluid that has absorbed the heat released by the reactor 202 during thenight-time refrigeration production phase or by the condenser 207 duringthe day-time reactor 202 regeneration phase, and secondly by condensingsaid working fluid, thus releasing the heat previously absorbed directlyto the outside air via the heat pipe condenser 702.

During the night, a heat pipe evaporator 701, incorporated into thetubular elements 501, is supplied with liquid working fluid and thuscools the reactor 202 by evaporation of the liquid working fluid. Thesteam produced in this way condenses at night-time ambient temperaturein a heat pipe condenser 702. The working fluid liquefied in this wayflows by gravity into the tank 705 by means of the connection via thetubing 707 between said tank 705 and the inlet of the heat pipecondenser 702.

During the day, the heat pipe evaporator 701 incorporated into thereactor 202 is inactive due to the closing of two valves 703, 704 placedbetween the evaporator 701 and the condenser 702 of the heat pipe loop.The first, 703, makes it possible to control the flow of the workingfluid through a liquid connection located at the bottom, while thesecond, 704, makes it possible to control the flow of the working fluidthrough a gas connection located at the top.

Thus, when the reactor 202 is heated by the sun during the regenerationphase, the pressure in the heat pipe evaporator 701, isolated in thisway, increases and causes the draining of the working fluid from thebottom of the evaporator 701 in liquid form. It is then stored in aworking fluid tank 705 by means of a drain line 709. Preferably, theworking fluid tank 705 is arranged to store the liquid working fluidduring the draining of the evaporator incorporated into the reactor. Thereactor 202 is thus arranged to increase in temperature and perform itsregeneration during the day.

With reference to FIGS. 7 and 9, the heat pipe loop for cooling thereactor 202 thus comprises:

-   -   a heat pipe evaporator 701 preferably comprising a tube 701        arranged inside the tubular elements 501 of the reactor 202 and        advantageously in close thermal contact with the solid reagent        material 502. The tubular elements 501 of a reactor 202, tilted        vertically, each comprise an evaporator tube 701 connected by        manifolds at the bottom and top;    -   a fluid condenser 702 of the heat pipe loop, preferably        comprising a set of finned tubes connected to each other by        manifolds and exchanging directly with the outside ambient air.        These finned tubes are preferably arranged horizontally at the        rear of the reactor 202, advantageously with a slight tilt        enabling the condensed working fluid to flow to a condensed        liquid working fluid tank 705;    -   a condensed liquid working fluid tank 705 the position of which        advantageously enables satisfactory filling of the evaporator        tubes 701 of the heat pipe loop with working fluid. According to        a particular embodiment, the working fluid is preferably        maintained at a minimum liquid working fluid level in the        evaporator tubes 701 of between one third and three quarters of        the height of the tube 701. According to another embodiment, the        liquid working fluid tank 705 also comprises the condenser 207        to condense the reactive gas released during the day by the        reactor 202 heated in the sun. The working fluid tank 705 thus        acts as an evaporator during the day. The working fluid steam        produced by the condensing of the reactive gas is then conveyed        to the condenser 702 via the pipe 707;    -   a device for regulating the flow of the working fluid in the        heat pipe loop, activated passively at the start and end of the        day and comprising:        -   a valve 704 between the liquid outlet 708 of the working            fluid tank 705 and the liquid inlet at the bottom of the            evaporator tubes 701, thus making it possible to supply them            with working fluid throughout the night and prevent them            from filling during the day;        -   a valve 703 placed on the steam pipe of the heat pipe loop,            between the steam outlet of the evaporator 701—at the            top—and the steam inlet of the condenser 702, thus making it            possible, at the start of the day, to block the passage of            the steam formed in the evaporator tubes 701 and cause a            pressure increase therein. This pressure increase makes it            possible to flush the working fluid contained in the            evaporator tubes 701 more efficiently and drain them by            means of a drain pipe 709 that opens into the expansion            space of the tank 705. This then enables a faster            temperature increase of the reactors 202 at the start of the            day and therefore more efficient heating of said reactors            202.    -   a valve 710 for starting the heat pipe loop (evacuation and/or        filling with working fluid).

According to a particular embodiment, the steam 703 and liquid 704valves close at the start of the day and open at the start of the nightindependently due to the action of autonomous control means theoperation of which is described with reference to FIGS. 8a and 8 b.

The autonomous control means of the valves 703 and 704 consists of athermostat bulb 801, heated during the day and cooled at night by anabsorbing plate 802 that has high solar absorptivity, high infraredemissivity and low thermal mass. The absorbing plate 802 is preferablyexposed to the sky to utilise both heating by solar radiation during theday and radiative cooling at night. The thermostat bulb 801 contains afluid that is arranged, under the action of solar radiation, to increasethe pressure in a bellows 803 and move a needle 804 on the seat of theport of the valve 703 or 704, thus closing off the passage of theworking fluid. When the pressure drops in the thermostat bulb 801, byradiative cooling at the start of the night, the bellows 803 reduces involume under the action of a spring 805 the stiffness of which can beadjusted by an adjusting screw 806. The needle 804 rigidly connected tothe bellows 803 detaches from the seat of the valve 703 or 704 and thenallows the working fluid to flow into the heat pipe loop.

Alternative Embodiment of the Device According to the Invention: aModular Design

According to a particular variant of the invention, compatible with anyone of the embodiments set out in the paragraphs above, and in order tofacilitate the implementation and installation of the device accordingto the invention, a modular design of the device according to theinvention is proposed.

With reference to FIGS. 10, 11 and 12, such a modular device comprisesat least two easily connectable assemblies:

-   -   a first assembly 1001 made up of several reactor modules 202,        201 as described above and each comprising the tubular elements        501 exposed to the sun, the condenser 207—preferably of the        ammonia type—and the first tank 208 the volume of which        corresponds to the capacity of the module, the device for        cooling the tubular elements 501 and the condenser 702, and the        means making it possible to control the flows of reactive gas        over the course of the day (valves 703, 704, 204, 205, solar        devices for controlling the ventilation flaps and/or the heat        pipe loop 706),    -   a second assembly 1002 incorporating the elements necessary for        refrigeration:        -   a cold chamber 215 comprising thermal insulation;        -   a liquid refrigerant tank 209 the volume of which preferably            corresponds to the daily refrigeration requirements of the            cold chamber 215. This tank comprises thermal insulation 210            in order to limit the thermal gain during the night-time            refrigeration phase, and liquid 1003 and steam 1005            connections comprising connecting valves 1004 to the            evaporator 212 placed in the cold chamber 215. Connections            1006 and 1007 to the valves 206 and 205 provide the            connection to the first assembly 1001;        -   an evaporator 212, preferably of the flooded type, and            advantageously supplied with refrigerant by thermosyphon            from the second liquid refrigerant tank 209 placed above.            The evaporator 212 is made up of tubes that are vertically            tilted and supplied with refrigerant from the bottom by a            manifold 1008. The steam produced is collected by a second            manifold 1009 placed in a higher position than the manifold            1008, so that the steam produced enables the conveyance and            natural circulation of the refrigerant in the evaporator            212;        -   a phase-change material 213 that makes it possible to store            the refrigeration produced and redeliver it on demand over            the course of the following day;        -   a connection equipped with a tight isolation valve 1010 that            makes it possible to start the whole device (evacuation and            filling with reactive gas).

The modularity of such a device makes it possible to connect a pluralityof first elements 1001 to at least one second element 1002.

Of course, the invention is not limited to the examples which have justbeen described and numerous adjustments can be made to these exampleswithout exceeding the scope of the invention. In particular, thedifferent characteristics, forms, variants and embodiments of theinvention can be combined with one another according to variouscombinations inasmuch as they are not incompatible or mutuallyexclusive. In particular all the variants and embodiments describedpreviously can be combined with each other.

1. An autonomous device for the production of refrigeration from alow-temperature solar thermal source between 50° C. and 130° C., saidrefrigeration being produced with a temperature difference 5° C. to 40°C. lower than ambient temperature and said device implementing a methodfor the thermochemical sorption of a refrigerant by a solid reagent,said device comprising: a reactor arranged to contain the solid reagentand comprising at least one heat exchanger to cool and/or heat saidreactor; a condenser capable of liquefying the gaseous refrigerantcoming from the reactor; a first tank for storing the liquid refrigerantproduced by the condenser at ambient temperature; an enclosure arrangedto store a phase-change material and also comprising an evaporator indirect contact with said phase-change material and capable ofevaporating the liquid refrigerant; a second tank for storing the liquidrefrigerant at a temperature lower than ambient temperature, connectedto the first tank on the one hand and the evaporator and the reactor onthe other hand; at least one means of conveying the refrigerant arrangedto circulate said refrigerant in liquid or gaseous form between thereactor, the first tank, the second tank and the evaporator; and atleast one means of controlling the flow of the refrigerant acting on themeans of conveying the refrigerant, said at least one control meansbeing arranged to regulate the flow of the refrigerant independently asa function of the pressures prevailing in the reactor, the first andsecond tanks, the condenser and the evaporator.
 2. The device accordingto claim 1, characterized in that the enclosure and/or the second tankare thermally insulated.
 3. The device according to claim 1,characterized in that the evaporator is supplied with liquid refrigerantfrom the second tank by the difference in the density of saidrefrigerant between the inlet and outlet of said evaporator.
 4. Thedevice according to claim 1, characterized in that the reactor alsocomprises an isothermal housing arranged to contain the heat exchangerand/or the reactor and capable of reducing the heat losses of saidreactor.
 5. The device according to claim 1, characterized in that thereactor is made up of a plurality of tubular elements comprising thesolid reagent and connected to each other by said means of conveying therefrigerant.
 6. The device according to claim 5, characterized in thatthe plurality of tubular elements is coated with a solar-absorbingcoating to improve the thermal efficiency of the plurality of tubularelements, said coating being in close contact with the wall of theplurality of tubular elements.
 7. The device according to claim 6,characterized in that the solar-absorbing coating has low infraredemissivity.
 8. The device according to claim 5, characterized in thatthe reactor also comprises at least one covering element transparent tosolar radiation, arranged to reduce the heat losses and enhance thesolar collection efficiency, said at least one covering elementextending beyond the surface of the reactor exposed to the sun.
 9. Thedevice according to claim 5, characterized in that at least one of thesurfaces of the reactor not exposed to the sun is thermally insulated inorder to reduce the heat losses.
 10. The device according to claim 5,characterized in that the reactor also comprises actuation means inorder to orient the plurality of tubular elements of the reactor in aplane substantially perpendicular to the direction of the sun and thuspresent the maximum possible solar-absorbing area.
 11. The deviceaccording to claim 8, characterized in that the night-time cooling ofthe reactor is provided by natural circulation of the air in thereactor.
 12. The device according to claim 11, characterized in that thereactor also comprises at least one flap for the ventilation of theplurality of tubular elements, said at least one flap being located atthe top and/or bottom of said reactor.
 13. The device according to claim12, characterized in that the at least one ventilation flap is arrangedto seal the reactor when it is in the closed position.
 14. The deviceaccording to claim 12, characterized in that the at least oneventilation flap also comprises drive means to open and/or close it. 15.The device according to claim 14, characterized in that the drive meansconsists of a low-power electric motor.
 16. The device according toclaim 15, characterized in that the electric motor is powered by anelectricity production and/or storage device.
 17. The device accordingto claim 14, characterized in that the drive means consists of a rackand pinion device actuated by a compressed air rotary jack connected toa compressed air reserve.
 18. The device according to claim 17,characterized in that the compressed air reserve is refilled by an aircompressor powered by photovoltaic panels.
 19. The device according toclaim 14, characterized in that the drive means consists of a rack andpinion device actuated by a single-acting hydraulic linear jackcontrolled by a thermostat bulb in thermal contact with an absorbingplate exposed to the sun.
 20. The device according to claim 11,characterized in that the plurality of tubular elements also comprises aplurality of circular fins the base of which is in close thermal contactwith the wall of the tubular elements in order to enhance the heatexchanges.
 21. The device according to claim 20, characterized in thatthe plurality of fins is covered with a solar-absorbing coating toenhance the heat exchanges.
 22. The device according to claim 11,characterized in that the plurality of tubular elements is arrangedhorizontally in order to improve the flow of air around said tubularelements.
 23. The device according to claim 11, characterized in thatthe condenser is of the finned tube exchanger type and cools, during theday, by natural air convection around said finned tubes.
 24. The deviceaccording to claim 5, characterized in that the night-time cooling ofthe reactor is provided by a heat pipe loop operating as a thermosyphonand comprising: a working fluid capable of performing thermodynamicwork, said working fluid propagating in the heat pipe loop by means ofat least one means of conveying; a so-called heat pipe evaporator,working in conjunction with the plurality of tubular elements of thereactor and arranged to evaporate the working fluid and absorb the heatreleased by the reactor; a so-called heat pipe condenser, working inconjunction with the evaporator and the reactor, said condenser beingarranged to liquefy the working fluid and perform a heat transfer withthe outside air; a working fluid tank arranged to store said liquidworking fluid and enable the optimum filling of the at least one tubularelement of the reactor with working fluid; a passive, autonomous devicefor controlling the flow of the working fluid in the heat pipe loopcomprising: a first working fluid flow control means, located betweenthe working fluid tank and the bottom of the at least one means ofconveying the working fluid, said first control means being arranged tocontrol the liquid working fluid supply to the at least one means ofconveying the working fluid; and a second working fluid flow controlmeans, located between the outlet of the heat pipe evaporator and theheat pipe condenser, arranged to control the movement of the gaseousworking fluid in the at least one means of conveying the working fluid.25. The device according to claim 24, characterized in that it alsocomprises a valve for starting the heat pipe loop, arranged to fill saidheat pipe loop with working fluid and/or drain it.
 26. The deviceaccording to claim 24, characterized in that the heat pipe evaporatorcomprises at least one means of conveying the working fluid arrangedinside the plurality of tubular elements of the reactor and in closethermal contact with the solid reagent, said at least one means ofconveying the working fluid associated with each tubular element beingconnected to each other by manifolds at the top and bottom.
 27. Thedevice according to claim 24, characterized in that the heat pipecondenser is made up of at least one finned tube connected to each otherby means of conveying the working fluid.
 28. The device according toclaim 27, characterized in that the at least one finned tube of the heatpipe condenser are arranged substantially horizontally at the rear ofthe reactor, with a slight tilt to enable the gravity flow of theliquefied working fluid to the working fluid tank.
 29. The deviceaccording to claim 24, characterized in that the working fluid tank isarranged to maintain a minimum working fluid level in the means ofconveying said working fluid of between one third and three quarters ofthe height of a tubular element of the reactor.
 30. The device accordingto claim 24, characterized in that the working fluid tank is arranged toevaporate the working fluid and also comprises the refrigerant condenserarranged to liquefy said refrigerant.
 31. The device according to claim24, characterized in that the device for controlling the flow of workingfluid in the heat pipe loop also comprises at least one autonomouscontrol means, arranged to respectively open and close the first andsecond working fluid flow control means.
 32. The device according toclaim 31, characterized in that the at least one autonomous controlmeans of the first and second working fluid flow control meanscomprises: an absorbing plate capable of absorbing solar radiation andemitting in the infrared, said absorbing plate being arranged to heat bymeans of day-time solar radiation and cool during the night; athermostat bulb in thermal contact with the absorbing plate, comprisinga fluid capable of expanding under the effect of a temperaturevariation; and a connecting element working in conjunction firstly withthe thermostat bulb and secondly with the first and/or second workingfluid flow control means, said connecting element being arranged to openor close said working fluid flow control means.
 33. The device accordingto claim 5, characterized in that it consists of a modular architecturemade up of: a plurality of first assemblies each comprising: the reactormade up of a plurality of tubular elements and comprising the heatexchanger; the condenser capable of liquefying the refrigerant; the tankfor storing the refrigerant at ambient temperature, the volume of whichcorresponds to the volume of the plurality of tubular elements of saidfirst assembly; refrigerant flow control means; a second assemblycomprising: the enclosure arranged to store a phase-change material andcomprising thermal insulation; the second tank for storing the liquidrefrigerant at a temperature lower than ambient temperature andcomprising thermal insulation; the evaporator for evaporating therefrigerant, located in the enclosure and working in conjunction withthe second tank; first means of controlling the flow of refrigerantbetween the evaporator and the second tank; and second means ofcontrolling the flow of refrigerant to ensure the connection between thesecond assembly and the plurality of first assemblies.
 34. The deviceaccording to claim 33, characterized in that the evaporator is of theflooded type and comprises at least one tubular element arranged tocirculate the refrigerant by thermosyphon with the second tank.
 35. Thedevice according to claim 33, characterized in that the second assemblycomprises a tight isolation valve, arranged to fill the device withrefrigerant and/or drain it.
 36. The device according to claim 1,characterized in that the refrigerant is ammonia.
 37. Use of the deviceaccording to claim 1 to produce refrigeration.
 38. Use of the deviceaccording to claim 1 to produce water.
 39. The use of the deviceaccording to claim 38, characterized in that water is produced bycondensing water vapour contained in the air on a wall kept cold by thedevice according to claim 1.